RFR: CODETOOLS-7903346: Cannot compile jtreg with jdk-19

[Iris Clark]

On Thu, 6 Oct 2022 00:03:12 GMT, Jonathan Gibbons <jjg at openjdk.org> wrote:

> Please review a trivial change to a class in the jtreg repo, to disable warnings on an "unintentionally serializable" class.
> The class extends `TreeMap` which happens to be `Serializable`, and the class contains some non-serializable fields.
> 
> In JDK 18, the javac serialization warnings were enhanced, causing this code to fail to compile with `-Xlint -Werror`.

Marked as reviewed by iris (Reviewer).

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PR: https://git.openjdk.org/jtreg/pull/129